1. The Field of the Invention
The present invention relates to apparatus for delivering relatively viscous materials to various surface types. More particularly, the present invention is ideally suited for applying dental agents, such as impression material, sealing, etching, bonding, restoring and/or other treatment agents, all hereinafter collectively referred to as dental agents, to teeth surfaces. This invention is also potentially useful in many other applications in addition to the field of dentistry, such as cosmetics, for example, applying fingernail polish, or electronic or mechanical assemblies requiring application of adhesives or coatings, to name just a few.
2. The Prior Art
Bonding agents play an important role in dental restorative techniques. Generally, bonding agents are applied to tooth surfaces in order to firmly attach a restoration to the tooth. When the restoration is a composite resin restoration, the composition of the bonding agent is usually that of the matrix of the composite resin.
Before applying a bonding agent, the enamel around a cavity preparation is etched with acid. Acid etching of enamel creates micro-irregularities on the enamel surface. The resin in the bonding agent is usually diluted with monomers so that it has a low viscosity which can readily penetrate into the microscopic irregularities and undercuts produced by the acid etching. The bonding agent is then polymerized. It is believed that when the composite restorative resin is inserted into the cavity, it will polymerize to the bonding agent present on the cavity surface. In this way, better adaptation to the enamel walls of the cavity is achieved with improved mechanical retention of the restoration.
Various devices have been used in the art for applying dental bonding agents to tooth surfaces. One device used to apply dental bonding agents is a small porous sponge or swabbing material. In practice, a quantity of bonding agent is applied to a transfer pad. A sponge is then grasped with forceps and dipped into the bonding agent. The wetted sponge is then rubbed across the tooth surface in order to apply the bonding agent.
The small sponges are disposable to prevent cross contamination. However, the sponges do not permit accurate application of the bonding agent. Frequently, the bonding agent is applied to surrounding surfaces which do not need treatment. Moreover, the rubbing action required to apply the bonding agent necessarily damages the fragile crystalline surface structure of the tooth formed during acid etching. Once the crystalline surface structure of the tooth is damaged, its bondability is reduced.
Another existing device for applying bonding agent to tooth surfaces is a small disposable brush tip. Like the sponge, the brush tip must be held with forceps or some other holding device. The brush tip is then dipped into a quantity of bonding agent placed on a transfer pad.
Like the sponge, the brush tip is disposable. In addition, the brush tip does not damage the fragile crystalline structure of the tooth surface produced by acid etching. However, like the sponge, the brush tip must constantly be rewetted by the bonding agent during the dental procedure. This action tends to incorporate tiny microbubbles. Moreover, the disposable brush tips used in the art usually have long bristles which do not form a fine tip. As a result, the bonding agent is often inadvertently applied to surrounding tooth surfaces.
Yet another device for applying bonding agents to tooth surfaces is a very fine paint brush. Such a brush can apply the bonding agent to tooth surfaces with precision and detail.
Despite its advantages, a paint brush must also be repeatedly dipped into a quantity of bonding agent during the procedure. In addition, a paint brush is difficult to properly sterilize and is usually nondisposable, thereby making it difficult for the dentist to maintain an aseptic environment. With the ever-increasing threat of Acquired Immune Deficiency Syndrome ("AIDS") in society, use of a nondisposable applicator which is also difficult to sterilize has become unacceptable.
Further, in each of the known devices for applying bonding agents to tooth surfaces, a quantity of bonding agent is placed on a transfer pad so that the device can be rewetted during the surgical procedure. Such a technique is not only wasteful, but it exposes the bonding agent to light, air, and airborne contaminants, light being significantly detrimental as most resin-based systems used by dentists are light activated.
Moreover, time is often of the essence in applying bonding agents to tooth surfaces, both to the dentist and due to working conditions such as when working on young children that may squirm, or in order to avoid contamination. As a result, it is important for bonding agents to be applied quickly and accurately. Thus, the need to constantly rewet the bonding agent applicator during the procedure is not only inefficient, but may reduce the effectiveness of the resulting bond between the restoration and the tooth surface. Many of these same problems exist when applying other types of dental agents.
In an attempt to solve many of these problems, an apparatus has been devised that includes a syringe-type dispenser for holding the quantity of dental agent and a removable applicator tip having bristles at one end. The bristles are in communication with the syringe-type dispenser, thereby allowing the dental agent to be continuously applied to the tooth surfaces without the need to stop the dental procedure and re-wet the applicator. This device is more particularly disclosed in my prior U.S. Pat. No. 4,997,371, incorporated herein by reference.
While this device is very effective and solves many of the problems discussed above, it has been found that there are still some problems that exist with that device. For example, the bristles which are held by the applicator tip are primarily held by the frictional grip which occurs at the distal end of the tip. This causes the bristles to act as a filter, particularly with respect to any filler particles that are contained in the dental agent. Such filtering may change the physical properties of the particular agent, such as a bonding agent and may make the actual bond weaker. Sometimes such filtering can even tend to choke off the delivery tip, preventing flow of material. In such cases, if a dentist does not use appropriate restraint, attempting to force the flow of material through a clogged tip may actually cause the tip to be blown off, expelling undesired quantities of the material into the patient's mouth.
Furthermore, in this type of device, the fiber count is critical because if there are not enough fibers, even to the extent that there are only two or three fibers too few, the bristles will tend to push back into the tip and will not be held by the frictional grip at the distal end. On the other hand, if too many fibers are included, so that even two or three fibers too many are found in the brush, the plastic material at the end of the tip will tend to split. This, of course, substantially complicates the manufacturing process, making it much more time consuming and tedious in order to assure very close tolerance on the fiber count in order to avoid the mentioned problems. Moreover, even if the fiber count is exact, the problem of filtering filler particles tends to remain.